Function _triangle_neighbors

mne/surface.py:408–423

Efficiently compute vertex neighboring triangles.

(tris, npts)

def _triangle_neighbors(tris, npts):
    """Efficiently compute vertex neighboring triangles."""
    # this code replaces the following, but is faster (vectorized):
    # neighbor_tri = [list() for _ in range(npts)]
    # for ti, tri in enumerate(tris):
    #     for t in tri:
    #         neighbor_tri[t].append(ti)
    rows = tris.ravel()
    cols = np.repeat(np.arange(len(tris)), 3)
    data = np.ones(len(cols))
    csr = coo_array((data, (rows, cols)), shape=(npts, len(tris))).tocsr()
    neighbor_tri = [
        csr.indices[start:stop] for start, stop in zip(csr.indptr[:-1], csr.indptr[1:])
    ]
    assert len(neighbor_tri) == npts
    return neighbor_tri


@jit()